THE ULTRASTRUCTURE OF HIPPOCAMPALCA1 AREA OF THE RAT AFTER STATUS EPILEPTICUS PROVOKED BY KAINIC ACID SYSTEMIC ADMINISTRATION

Abstract

The ultrastructure of hippocampal CA1 area was investigated in rats 14 days after status epilepticus was induced by kainic acid. The structural alterations were found in 40% of the cells, predominantly in interneurons, which demonstrated both reversible changes (mitochondria with a dilated space between cristae and electron-dense matrix or mitochondria with few short cristae and moderately widened rough endoplasmic reticulum [RER] cisterns with few ribosomes) and more significant alterations (swollen mitochondria containing single dilapidated cristae, including those with damaged mitochondraial membranes, pathologically dilated RER profiles and focal or peripheral chromatolysis. In the areas subjected to chromatolysis, the membrane-like inclusions and vacuoles were sometimes observed. Besides, large osmiophilic irregular structures, surrounded by astrocyte processes rich in glycogen granules and gliofibrills, were rarely found in the neuropil. The synaptic architectonics was also changed. Asymmetrical synapses on small dendrites and spines containing osmiophilic postsynaptic zone were frequently observed. Their synaptic endings contained numerous synaptic vesicles and large vesicles with a central dense core. Some part of presynaptic endings showed clear signs of a classical dark-type degeneration. As in all the altered neurons the nucleus remained intact, we suggest that after status epilepticus the majority of the cells underwent the necrotic-type pathological changes.

Keywords

hippocampus / area CA / kainic acid / ultrastructure / status epilepticus

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